Overview

The Pharos is a newly-developed smart antenna. Unlike conventional omni-directional antennas that waste energy in all directions, the Pharos concentrates the available power where you need it most. Working in conjunction with pixhawk autopilot (a version with its own autopilot is being also developed), the antenna activates the side facing your UAV, boosting reception and range. A second Pharos can also be used on the aircraft, quadrocopter or UAV, keeping ground control in aim at all times. The Pharos is also circular-polarized, granting immunity to polarization losses and multipathing signals, an optimum choice for challenging environments.

Fund us on Kickstarter!

Background

Omni-directional antennas are used extensively with drones since they radiate and receive in all directions. The omni antennas were the only choice for unmanned systems as the drones are constantly changing directions and orientations due to their motion.

Only an omni antenna ensures that the drone’s ground station will be constantly under the antenna uniform coverage, regardless of the drone’s flight or ground track. Omni antennas might offer wide spatial coverage, but this comes at a cost. The main disadvantage of the omni antennas is their reduced gain, since the radiated power is distributed uniformly in all directions. Only a fraction of the radiated power is exchanged between the drone and its ground station and the biggest part gets wasted in all other directions. As a result, the radiated efficiency is usually less than 5% and that’s the main reason the data link between the drone and its ground station becomes unstable, weak, and finally breaks at ranges beyond 1 or 2 km with the current technology antennas. This is the cost for being able to cover all directions around the drone or the ground station.

It is an axiom that if we wish to increase the antenna’s radiated power (known as antenna gain), we have to reduce its radiation beam angle. As the beam angle decreases, the gain increases. This provides a greater coverage distance, but with a reduced coverage angle. If for example, we use a directional antenna on board the drone, it is not possible to keep the directional beam constantly pointed to the ground station as the drone moves arbitrarily. As soon as the drone’s antenna beam points away from the ground station, the link will break.

The Pharos Project

The Pharos antenna is the first antenna for drones and robotic platforms that forms a directional, high gain beam and keeps it always pointed to the drone control station, regardless of the drone’s motion. It can be used on both sides of the link, the ground control station and the drone. It is an electronically-controlled tracking antenna with no moving parts.

Key Features

Small but powerful

Small and lightweight

Lightweight

Weighting only 65 gr (2.3 oz) and with a size of 7x7x7cm it fits the smallest drones without negatively affecting their flight time.

Maximum Range - Minimal Power

Draws minimal power from the drone battery (18mA)

Smart Antenna

Integrated antenna switching logic

Long Range

Insane distance coverage (2.5x or 5x the range) depending on if it is used on one end or both ends of the link compared to omni-directional antennas.

Pharos Antenna Versions

The Pharos Antenna can be used on both the Drone and the Ground control station (GCS).

To use the Pharos Antenna with your Drone:

Plug the antenna 3-pin connector using a servo cable to the Pixhawk autopilot AUX-2 port. It draws power and it is controlled by the Pixhawk AUX-2 signal pin

Plug your drone transmitter to the antenna SMA connector (SMA plug).

Note:

The Pharos Antenna will use the drone’s Home Point as a reference point for diverting its beams. As the antenna beams will be directed towards the Home point, naturally, the Ground Control Station shall be in that area.

A custom Pixhawk firmware is offered that adds the Pharos Antenna functionality on top of the standard Pixhawk firmware.

To use the Pharos antenna with your Ground Control Station:

Use a Pixhawk autopilot with external GPS/compass and plug the Pharos antenna to the Pixhawk autopilot AUX-2 port just like the aerial version.

Plug your drone receiver to the antenna SMA connector (SMA plug).

As soon as you establish a telemetry link between the GCS and the drone using the Mission Planner the GCS Pharos antenna will divert its beams towards the drone.

Note:

The Pixhawk used on the GCS side requires loading a custom firmware version to it. This custom version will be available for download.

A firmware version that runs on the inexpensive Teensy board will also be offered with schematic diagrams for connecting your own GPS and IMU as an alternative GCS antenna controller.

Tip: To get the most out of the Pharos Antenna, you can use the 5.8 GHz Microhard Digital Data Link modems for streaming both telemetry and video through a single modem. This way, only one antenna is used for each modem for extend the range of both video and telemetry through a single, tiny deviceas shown to the right.

How to use the Pharos Antenna with the Microhard modems

How to use the Microhard 5.8GHz modem for streaming both telemetry and video from/to your drone and GCS

We have developed a carrier board for the 5.8GHz microhard modem that allows you to connect both the telemetry serial channel and an IP camera and stream both through the same channel. This set up, allows using a single Pharos antenna for streaming both video and telemetry!
The Pixhawk autopilot and IP cameras can be plugged directly as they are natively supported (plug-n-play) by the modem carrier board. To use an analogue camera you need to inject an analogue-to-IP converter in between (offered as an optional accessory). The schematic below shows how to connect the Microhard modem carrier board to the Pixhawk autopilot and an IP or analogue camera on your drone and on your Ground Control station to stream both video and telemetry using a single modem on each side and a single Pharos antenna.

The benefits of this set up are:

Reduced weight and size as a single modem and a single antenna is used for both video and telemetry on each side (no separate radios and antennas for telemetry and video).

Extreme data link range and data quality for both video and telemetry as this set up combines both data links into a single stream that is transmitted through the optimized Pharos digital antenna.

No moving parts (i.e. motors) for tracking antennas on both the drone and the GCS. The Pharos digital technology ensures robustness and ease of use on both ends.

As the video received by the GCS laptop is digital by nature (or digitized through the optional analogue-to-IP video converter) it can be used in a variety of new applications i.e. image processing, object recognition and tracking, etc.

As a sample of the endless possibilities, we have developed a new video projection technique called “video georeferencing”. This technique allows to correlate the received video location and orientation with the underlying 3D map and achieve unsurpassed Situational Awareness of where the drone video camera is pointing and where the actual objects shown in the video stream are geolocated in real time. Furthermore, it allows extracting real time geographic coordinates from any object appearing on the video window. A sample video showing the video georeferncing technique can be seen below.

Possible uses of the Pharos antenna are:

Use the Pharos antenna with a 5.8GHz video transmitter on the Pixhawk equipped drone (aerial side for improving video transmission)

Use the Pharos antenna with a 5.8GHz video receiver on the Ground by interfacing it to a Pixhawk controller (Ground side for improving video reception)

Use the Pharos antenna in conjunction with a Microhard 5.8GHz modem on both the drone and the GCS for improving both telemetry and video streaming.

The Pharos antenna can be used with any type of drone i.e. aerial, land based (rovers) or maritime (boats) to extend the range of your system. It is suitable for any robotic platform that needs an extended and robust data link.